In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. It is more specific than the general term electromagnetic spectroscopy in that it deals with visible light, near-ultraviolet, and near-infrared, but does not cover time-resolved spectroscopic techniques.

Spectrophotometry uses photometers that can measure a light beam’s intensity as a function of its color (wavelength). Important features of these instruments are spectral bandwidth (the range of colors it can transmit through the test sample), the percentage of sample-transmission, the logarithmic range of sample-absorption, and sometimes a percentage of reflectance measurement.

A common spectrophotometer use is for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass, or gases. However they can also be designed to measure the diffusivity on any of the listed light ranges that usually cover around 200 nm – 2500 nm using different controls and calibrations. Within these ranges of light, calibrations are needed on the machine using standards that vary in type depending on the wavelength of the photometric determination.

An example of an experiment in which spectrophotometry is used is the determination of the equilibrium constant of a solution. A certain chemical reaction within a solution may occur in a forward and reverse direction where reactants form products and products break down into reactants. At some point, this chemical reaction will reach a point of balance called an equilibrium point. In order to determine the respective concentrations of reactants and products at this point, the light transmittance of the solution can be tested using spectrophotometry. The amount of light that passes through the solution is indicative of the concentration of certain chemicals that do not allow light to pass through.

Application & Types

The use of spectrophotometers spans various scientific fields, such as physics, materials science, chemistry, biochemistry, and molecular biology. They are widely used in many industries including semiconductors, laser and optical manufacturing, printing and forensic examination, as well in laboratories for the study of chemical substances. Ultimately these tools are able to determine, depending on the control or calibration, what substances are present in a target and exactly how much through calculations of observed wavelengths.

More specifically, spectrophotometry is an important technique used in many biochemical experiments that involve DNA, RNA, and protein isolation, enzyme kinetics and biochemical analyses. A brief explanation of the procedure includes comparing the absorbency of a blank sample that does not contain a colored compound to a sample that contains a colored compound. The spectrophotometer is used to measure colored compounds in the visible region of light (between 350 nm and 800 nm), thus it can be used to find more information about the substance being studied. In biochemical experiments, a chemical and/or physical property is chosen and the procedure that is used is specific to that property in order to derive more information about the sample, such as the quantity, purity, enzyme activity, etc. It is also a helpful procedure for protein purification and can also be used as a method to create optical assays of a compound. Because the reader measures the wavelength of a compound through its color, a dye binding substance can be added so that it can undergo a color change and be measured. These instruments have been developed and improved over decades and have been widely used among chemists. It is considered to be a highly accurate instrument that is also very sensitive and therefore extremely precise, especially in determining color change. This method is also convenient for use in laboratory experiments because it is an inexpensive and relatively simple process.

UV-Vis The most common spectrophotometers are used in the ultraviolet and visible regions of the spectrum, and some of these instruments also operate into the near-infrared region as well.

Visible region 400–700 nm spectroscopy is used extensively in colorimetry science. It is a known fact that it operates best at the range of 0.2-0.8 O.D. Ink manufacturers, printing companies, textiles vendors, and many more, need the data provided through colorimetry. They take readings in the region of every 5–20 nanometers along the visible region, and produce a spectral reflectance curve or a data stream for alternative presentations. These curves can be used to test a new batch of colorant to check if it makes a match to specifications, e.g., ISO printing standards.

Traditional visible region spectrophotometers cannot detect if a colorant or the base material has fluorescence. This can make it difficult to manage color issues if for example one or more of the printing inks is fluorescent. Where a colorant contains fluorescence, a bi-spectral fluorescent system is used. There are two major setups for visual spectrum machines, d/8 (spherical) and 0/45. The names are due to the geometry of the light source, observer and interior of the measurement chamber. Scientists use this instrument to measure the amount of compounds in a sample. If the compound is more concentrated more light will be absorbed by the sample; within small ranges, the Beer-Lambert law holds and the absorbance between samples vary with concentration linearly. In the case of printing measurements two alternative settings are commonly used- without/with UV filter to control better the effect of UV brighteners within the paper stock.

Samples are usually prepared in cuvettes; depending on the region of interest, they may be constructed of glass, plastic (visible spectrum region of interest), or quartz (far UV spectrum region of interest).

IR The spectrophotometers designed for the infrared region are quite different because of the technical requirements of measurement in that region. One major factor is the type of photosensors that are available for different spectral regions, but infrared measurement is also challenging because virtually everything emits IR light as thermal radiation, especially at wavelengths beyond about 5 μm.

Another complication is that quite a few materials such as glass and plastic absorb infrared light, making it incompatible as an optical medium. Ideal optical materials are salts, which do not absorb strongly. Samples prepped for IR may be smeared between two discs of potassium bromide or ground with potassium bromide and pressed into a pellet. Where aqueous solutions are to be measured, insoluble silver chloride is used to construct the cell.

Customized Spectrophotomer Leases to Meet Your Needs

Operating Lease

This off-balance sheet financing structure provides three options at the end of the term. The lessee has the option to return the equipment to the lessor, renew at a discounted rate, or purchase the instrument for the fair market value. Monthly payments are also 100% tax deductible which yields additional cash savings.

Sale Leaseback

If you recently purchased equipment, Excedr can offer you cash for your instrument and convert your purchase into a long-term rental. This is called a sale leaseback. If you’ve paid for equipment within the last ninety days, we can help you recoup your investment and allow you to make low monthly payments. This also frees up cash in your budget rather than tying it down to the instrument.

Effect on Credit & Operating Capital

Leasing/renting does not hinder your future borrowing ability and allows you to keep your business credit line open for expansions, staffing, and other operational expenses. Additionally, it strengthens the cash flow of your business and keeps cash reserves free for business development opportunities.

Used Equipment

Unlike traditional financing and leasing companies, the Excedr program can accommodate refurbished/reconditioned equipment in addition to demo units. If you are looking for additional cost-savings, we recommend considering this option.

Speed of Approval

Excedr’s program allows you to respond quickly as your need for equipment and technology arises. You can be approved with minimal documentation and have the equipment you need in operation and generating revenue for your business quickly.

CONTACT US TODAY

No matter if you’re looking to lease a cryostat or leaseback a spectrophotomer, we can be of assistance. We want to provide you with exactly what you’re looking for, so call us at +1(510) 982-6552 or fill out the contact form to find out how we can help.